The samples were from the VA network. That’s why the “veterans” quote. The VA network tracks veterans under their care regardless of relocation. Civilian hospitals might not tracks someone who moves to a different state.
VA studies from day 1 of Covid have been superb.
VA in my area gave J&J in March. The gave it locally and we didn’t have to drive the 50 miles to the VA Hospital. According to this post my Vax status has been near zero for the last 7 months. The VA has said little about boosters and are not offering any locally.